A fluid control valve is one that intervenes between an upstream side flow path and a downstream side flow path, to control a flow rate or pressure of fluid flowing through the flow paths, or to close so as to prevent the fluid from flowing between the flow paths. For example, a normal close type fluid control valve has a diaphragm structure that separates a flow path and the outside from each other in the fluid control valve, and is configured to control a flow rate or pressure of fluid in such a way that an actuator arranged on the outside changes, of a valve seat member and a valve element member arranged on the flow path side, a position of the valve element member through the diaphragm structure.
More specifically, the diaphragm structure is configured to include: a thin film part; and a pin that is welded and protruded toward the flow path side in a direction normal to the thin film part and in abutting contact with the valve element member. Further, the actuator presses the pin from the outside to thereby elastically bend the thin film part, and consequently moves the pin toward the valve element member side to change the position of the valve element member (see Patent Literature 1).
Meanwhile, in recent years, a large diameter fluid control valve that can pass a large amount of fluid per unit time and also has a large controllable flow rate range has been required. For this reason, it is necessary to make a movable stroke of the pin moved by the actuator larger than in conventional designs to make it possible to control an opening level between the valve seat member and a valve element member in a wider range.
For example, in the case of attempting to make a movable stroke of the valve element member larger without changing an output of the actuator from a conventional specification, it is possible to decrease rigidity in the thin film part to lower repulsiveness.
However, the diaphragm structure has been fabricated by machining such as cutting in the past, and therefore, for example, in the case of attempting to form the thin film part thinner than in conventional fluid control valves to achieve the lower repulsiveness, highly accurate cutting is required, thereby increasing manufacturing cost.
Also, even in the case of being able to cut and form the thin film part by machining down to a thinness thin enough to achieve the required low repulsiveness, a probability of giving rise to defects such as forming cavities in the thin film part is increased, increasing a probability of being unable to fulfill a function as the diaphragm structure, such as giving rise to a fault that causes fluid leakage. For this reason, to eliminate defective products, the presence or absence of a cavity should be strictly inspected by X-ray inspection or the like, and therefore quality control cost is also increased.
Due to the abovementioned problems, and from the perspectives of processing accuracy and various types of costs, it is very difficult to give lower repulsiveness to the diaphragm structure by conventional machining.
In addition, in the case of the conventional structure like welding the pin normally to the thin film part, distortion occurs in a welding part, and as a result of repetitive operation, fatigue fracture is highly likely to occur. That is, the conventional configuration itself also becomes a partial factor for preventing lowering repulsiveness of the diaphragm structure and increasing a diameter of the fluid control valve.
Further, in order to increase the stroke without increasing the output from the actuator even while forming the thin film part with the same thinness as is conventional, it is possible to increase an area of the thin film part to increase an area to be deformed, and thereby increase a bending deformation amount from a supported part to the pin. However, in the case of increasing the area of the thin film part, an area that receives, of pressure received from fluid present on a side where the pin is protruded, pressure in a direction normal to the thin film part, i.e., in a direction opposite to a moving direction of the pin, is increased, and therefore an amount by which force applied from the actuator is compensated is also significantly increased. For this reason, simply increasing the area of the thin film part may result in a reduction in stroke amount instead.